Ionic Liquids Induced Structural Changes of Bovine Serum Albumin in Aqueous Media: A Detailed Physicochemical and Spectroscopic Study

Structural changes of a globular protein, bovine serum albumin (BSA), as a consequence of interaction with the surface active ionic liquids (ILs)-3-methyl-1-octylimidazolium chloride, [C(8)mim][Cl], and 1-butyl-3-methylimidazolium octylsulfate, [C(4)mim][C8OSO3]-have been investigated using various physicochemical and spectroscopic techniques such as tensiometry, conductometry, steady-state fluorescence, far-UV circular dichroism spectroscopy (CD), and dynamic light scattering (DLS). The interactional behavior of ILs (monomers and self-assembled structures) toward BSA in different IL concentration regimes at the air/solution interface as well as in the bulk is investigated and discussed depending upon the nature of ions of ILs. CD combined with the steady state fluorescence spectroscopy provided valuable insights into the unfolding of BSA as a consequence of IL binding. The complementary results obtained from the multitechnique approach proved very useful in drawing out the mechanism of interaction between ILs and BSA in different IL concentration regimes.